Unmanned aerial vehicles (UAVs) vary in degrees of sophistication. For example, UAVs used by hobbyists often rely completely on receipt of control signals from a user-operated remote control device. Thus, these UAVs rely on a user to provide all navigational instructions. More advanced UAVs may determine some navigational instructions without direct input. These UAVs may receive high level instructions (such as waypoints, a destination, and/or other parameters), and may implement logic to navigate through airspace based on the high level instructions and other information accessed by sensors on the UAVs. For example, some UAVs may access global positioning satellite (GPS) systems to access current location information while some UAVs may communicate with a command station using a mobile telephone network to exchange information, log progress, and for other reasons.
Many regions of land and portions of airspace do not have reliable access to GPS signals and/or to mobile telephone networks. For example, some remote rural areas, some wilderness areas, and some areas that frequently experience inclement weather, such as heavy precipitation, may not have reliable access to GPS signals and/or reliable access to mobile telephone networks. This may pose navigational problems for UAVs that enter these regions of land and portions of airspace when the UAVs rely on GPS or mobile telephone networks for at least some navigation or control instructions.